On Fri, Jul 25, 2025 at 11:54:29AM +0200, Igor Mammedov wrote:
> test is to be used for benchmarking/validating HPET main counter reading
>
> how to run:
> QEMU=/foo/qemu-system-x86_64 x86/run x86/hpet_read_test.flat -smp X
> where X is desired number of logical CPUs to test with
>
> it will 1st execute concurrent read benchmark
> and after that it will run torture test enabling/disabling HPET counter,
> while running readers in parallel. Goal is to verify counter that always
> goes up.
>
> Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
> ---
> v4:
> * use global for test cycles and siplify code a bit
> * use cpu number instead of APCI ID as index into latency array
> * report failure if a cpu measured 0 latency
> * replace on_cpus() with on_cpu_async() to avoid BSP
> interrupting itself
> * drop volatile
>
> v3:
> * measure lat inside threads so that, threads startup time wouldn't
> throw off results
> * fix BSP iterrupting itself by running read test and stalling
> other cpus as result. (fix it by exiting read test earlier if
> it's running on BSP)
> v2:
> * fix broken timer going backwards check
> * report # of fails
> * warn if number of vcpus is not sufficient for torture test and skip
> it
> * style fixups
> ---
> x86/Makefile.common | 2 +
> x86/hpet_read_test.c | 93 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 95 insertions(+)
> create mode 100644 x86/hpet_read_test.c
>
> diff --git a/x86/Makefile.common b/x86/Makefile.common
> index 5663a65d..ef0e09a6 100644
> --- a/x86/Makefile.common
> +++ b/x86/Makefile.common
> @@ -101,6 +101,8 @@ tests-common += $(TEST_DIR)/realmode.$(exe) \
> realmode_bits := $(if $(call cc-option,-m16,""),16,32)
> endif
>
> +tests-common += $(TEST_DIR)/hpet_read_test.$(exe)
> +
> test_cases: $(tests-common) $(tests)
>
> $(TEST_DIR)/%.o: CFLAGS += -std=gnu99 -ffreestanding -I $(SRCDIR)/lib -I $(SRCDIR)/lib/x86 -I lib
> diff --git a/x86/hpet_read_test.c b/x86/hpet_read_test.c
> new file mode 100644
> index 00000000..a44cdac2
> --- /dev/null
> +++ b/x86/hpet_read_test.c
> @@ -0,0 +1,93 @@
> +#include "libcflat.h"
> +#include "smp.h"
> +#include "apic.h"
> +#include "asm/barrier.h"
> +#include "x86/atomic.h"
> +#include "vmalloc.h"
> +#include "alloc.h"
> +
> +#define HPET_ADDR 0xFED00000L
> +#define HPET_COUNTER_ADDR ((uint8_t *)HPET_ADDR + 0xF0UL)
> +#define HPET_CONFIG_ADDR ((uint8_t *)HPET_ADDR + 0x10UL)
> +#define HPET_ENABLE_BIT 0x01UL
> +#define HPET_CLK_PERIOD 10
> +
> +#define TEST_CYCLES 100000
> +
> +static atomic_t fail;
> +static uint64_t latency[MAX_TEST_CPUS];
> +
> +static void hpet_reader(void *data)
> +{
> + long i;
> + uint64_t old_counter = 0, new_counter;
> + long id = (long)data;
> +
> + latency[id] = *(uint64_t *)HPET_COUNTER_ADDR;
> + for (i = 0; i < TEST_CYCLES; ++i) {
> + new_counter = *(uint64_t *)HPET_COUNTER_ADDR;
> + if (new_counter < old_counter)
> + atomic_inc(&fail);
> + old_counter = new_counter;
> + }
> + /* claculate job latency in ns */
> + latency[id] = (*(uint64_t *)HPET_COUNTER_ADDR - latency[id])
> + * HPET_CLK_PERIOD / TEST_CYCLES;
> +}
> +
> +static void hpet_writer(void *data)
> +{
> + int i;
> +
> + for (i = 0; i < TEST_CYCLES; ++i)
> + if (i % 2)
> + *(uint64_t *)HPET_CONFIG_ADDR |= HPET_ENABLE_BIT;
> + else
> + *(uint64_t *)HPET_CONFIG_ADDR &= ~HPET_ENABLE_BIT;
> +}
> +
> +int main(void)
> +{
> + unsigned long cpu, time_ns, lat = 0;
> + uint64_t start, end;
> + int ncpus = cpu_count();
> +
> + do {
> + printf("* starting concurrent read bench on %d cpus\n", ncpus);
> + *(uint64_t *)HPET_CONFIG_ADDR |= HPET_ENABLE_BIT;
> + start = *(uint64_t *)HPET_COUNTER_ADDR;
> +
> + for (cpu = cpu_count() - 1; cpu > 0; --cpu)
> + on_cpu_async(cpu, hpet_reader, (void *)cpu);
> + while (cpus_active() > 1)
> + pause();
> +
> + end = (*(uint64_t *)HPET_COUNTER_ADDR);
> + time_ns = (end - start) * HPET_CLK_PERIOD;
> +
> + for (cpu = 1; cpu < ncpus; cpu++)
> + if (latency[cpu])
> + lat += latency[cpu];
> + else
> + report_fail("cpu %lu reported invalid latency (0)\n", cpu);
> + lat = lat / ncpus;
> +
> + report(time_ns && !atomic_read(&fail),
> + "read test took %lu ms, avg read: %lu ns\n", time_ns/1000000, lat);
> + } while (0);
> +
> + do {
> + printf("* starting enable/disable with concurrent readers torture\n");
> + if (ncpus > 2) {
> + for (cpu = 2; cpu < ncpus; cpu++)
> + on_cpu_async(cpu, hpet_reader, (void *)TEST_CYCLES);
> +
> + on_cpu(1, hpet_writer, (void *)TEST_CYCLES);
> + report(!atomic_read(&fail), "torture test, fails: %u\n",
> + atomic_read(&fail));
> + } else
> + printf("SKIP: torture test: '-smp X' should be greater than 2\n");
> + } while (0);
Nitpick: IMHO the "do... while" indentation isn't strictly needed. Maybe
it implies the blobs can be put separately into two functions, e.g. as
test_hpet_concurrent_ro() / test_hpet_concurrent_rw().
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> +
> + return report_summary();
> +}
> --
> 2.47.1
>
--
Peter Xu
